For historical and circumstantial reasons the Greeks for many centuries developed a supranational conscience and preferred to identify themselves solely as Christians, especially during the centuries of captivity under the Turks. It is significant that although the patriarchs of Constantinople and many bishops of the Bulgarians, Albanians, and Slavs were Greeks during the Ottoman period, they did not attempt to Hellenize their congregations: neither did they try to force them to abandon their liturgical traditions and cultures. Of course, every rule has its exceptions. The fact is, however, that the tradition of the Greek Church has been one of religious toleration rather than nationalism. If this had not been true, the Greek Church, in the Byzantine centuries and especially during the four hundred years under the Turks, could have Hellenized all the minorities under her aegis or at least a great majority of them. The Greek historian K. Paparigopoulos, known for his patriotism, blamed the Church for not exploiting here numerous opportunities to Hellenize the various Balkan peoples in a period of four hundred years, something she could have done without much difficulty.

The term "Hellene" as an ethnic name began to appear among the Greeks of the high Middle Ages, but still was not commonly used. However, all nations living outside the medieval Greek world of the Byzantine Empire, such as the Russians, the Germans, Khazars, the English, the Georgians, the peoples of Italy, and the Franks, called the native inhabitants of the Byzantine Empire "Greeks." The designations "Greek Orthodox" and "Roman Catholic" were unknown in the early and medieval Church, and they took on their distinct meaning only after the eleventh century.

Nevertheless, it was Greeks, or Hellenized missionaries, both those of the Asiatic dispersion and those of the European continent, who played a leading role in the history of Christianity. Antioch, Tarsus, Ephesus, Smyrna, Philippi, Thessaloniki, Athens, Corinth, Nikopolis, the islands of Cyprus and Crete, were only a few of the many Greek cities and territories that heard the Christian gospel. All the important churches of the first three centuries were Greek or Greek-speaking. Besides Saint Paul, other Apostles such as Andrew, John the Evangelist, Philip, Luke, Mark, Titus, labored for the Christianization of the Greeks. As early as the second century there were flourishing churches not only in the cities just mentioned but also in such lesser Greek towns as Megara, Sparta, Patras, Larissa, Melos, Tenos, Paros, Thera, and Chios.

Many of these Greek cities produced great martyrs and profound thinkers during this period. Men such as Polycarp, Ignatios, Aristides, Athenagoras, Anakletos (bishop of Rome where he is listed as Anacletus), Clement of Alexandria, Origen, Gregory the Illuminator of the Armenians, Justin, and Melito of Sardis were either Greek or Hellenized; some were born in the city of Athens or educated there. On the other hand, the persecutions of the Christians under the Roman emperors Nero, Domitian, Trajan, Marcus Aurelius, Galerius, Diocletian affected the Greek East much more than the Western Roman Empire. Dionysios, bishop of Athens, Aristios of Dyrrahion, Nikephoros, Cyprian, Dionysios, Anekitos, Parilos, Leonidas, Irene, Demetrios, Catherine, Zeno, Eusebius, Zoukos, Theodoulos are only a few of the thousands of martyrs of such places as Corinth, Athens, Thessaloniki, Gortyn in Crete, Philippi, and Kerkyra (Corfu). It was their blood that nourished the Christian seed, as Tertullian observed. The first period in the history of the Church ended with the edict of toleration in 313 under Constantine the Great, which prepared the way for Christianity to become the state religion of the later Roman and Byzantine empires.